1. Field of the Invention
This invention relates to a process for producing a thermal stencil master sheet for stencil printing. More particularly it relates to a process for producing a thermal stencil master sheet having improved perforation properties.
2. Description of the Related Art
There has been known a thermal stencil master sheet obtained by laminating a thermoplastic resin film onto a porous substrate such as a porous thin paper and further providing a release agent layer on the surface of the film for preventing melt-adhesion of the film to a manuscript or a thermal head. In the case where stencil making is carried out using such a thermal stencil master sheet a manuscript is closely attached onto the surface of the film of the stencil master sheet, followed by irradiating infrared rays or a xenon flash light thereto from the side of the perforated substrate of the thermal stencil master sheet to generate heat at the black image part of the manuscript, melt-perforating the film of the thermal stencil master sheet by the generated heat and thereafter stripping the manuscript from said stencil master sheet. Alternatively, the image of a manuscript is read by an image sensor, followed by melt-perforating the film of said stencil master sheet by the heat of thermal head just as the image is.
For improvement of the perforation properties of the thermal stencil master sheet, a process of making the material of the thermoplastic film easy to be perforated by heat and a process of making the thermoplastic film thinner have been proposed.
However, when such processes are employed, a problem has been raised that the mechanical strengths such as tensile strength of the thermoplastic film itself are reduced so that it is liable to be broken when it is laminated on the porous substrate, for example.